A shed or prefab garage is only as good as what it sits on. A pad that is level, drained and compacted keeps the doors closing and the floor dry for decades; one built on topsoil heaves the first winter. Here is how to build it right.
Permits first
In Ontario, most accessory buildings over 15 square metres (about 160 square feet) need a building permit, and every municipality has setback rules from property lines and, on rural lots, from the septic bed and well. Garages with a slab often need a permit regardless. Check with your township before you pick the spot. If you are near water or a wetland, the conservation authority may also have a say.
Pick the spot for water, not convenience
Put the pad on the highest practical ground, and never in the low corner where water collects. Slope the surrounding ground away from the pad on every side.
Step 1: Locates and layout
Ontario One Call locates are free and required by law before digging. Mark the pad about two feet larger than the building on each side so there is a gravel apron for drainage and for working.
Step 2: Strip the topsoil
Remove all sod and topsoil down to firm subsoil, usually six to twelve inches, with the SVL75-3 track loader or, for a small shed, the BX23s tractor. Organic soil never compacts and is the cause of nearly every sunken shed.
Step 3: Excavate to depth
For a shed on skids or blocks, a six inch gravel base is plenty. For a garage or workshop with a concrete slab, the slab needs a compacted granular base under it and, in this climate, either a thickened edge or frost walls depending on the design and the permit, so follow the drawings. Dig with the loader on flat ground; use the U17 if frost wall trenches are required.
Step 4: Fabric, base and compaction
On clay, lay geotextile fabric. Spread three quarter inch clear stone or crusher run in lifts of no more than four inches, compacting each lift with a plate compactor. Clear stone drains and does not heave; crusher run locks tight and is easier to level for a slab. Many builders use a clear stone base with an inch of screenings on top to set blocks or forms.
Step 5: Level
Check with a long straightedge and a level, or a laser. A quarter inch over ten feet is a good target for a shed on blocks; a slab wants the forms dead level.
Machines and materials
A 12 by 16 shed pad, 16 by 20 including the apron, at six inches deep needs about ten to twelve tonnes of gravel. A 24 by 24 garage pad needs closer to forty. The loader spreads either in an hour. Weekend rental of the SVL75-3 is $600 and the BX23s is $350, delivered across Georgina, York, Durham and Kawartha Lakes.
Call or text 905-251-2521 with the building size and we will tell you which machine and how much gravel to order.